Current nuclear medicine techniques utilized in cardiovascular imaging are limited by camera performance. Spatial resolution limitations are encountered when imaging with low photon energies from isotopes such as 201Tl and 133Xe. Data rate limitations are encountered when imaging with first pass indicators such as 99mTc. Existing isotopes due to the half life of several hours to several days, contribute unnecessary dose to the patient. The long half life limits the number of views that can be taken in first past ventricular function measurements. A new generator-produced isotope, 178Ta, with a half life of 9.3 min. and photon energy to 60 keV, has recently been shown to be of value in heart studies. A high pressure multiwire counter (MWPC) can replace the Anger Camera in all the above cardiovascular studies which use isotopes with photon energies below 100 keV. This will result in improvement in spatial resolution, improved data rate capabilities and in the case of 178Ta, first pass studies, lower dose to the patient per given study. The proposed chamber would operate at 10 atm pressure with a xenon-methane gase mixture. Purification techniques would be used that allowed sealed chamber operation for up to one year of operation. Intrinsic spatial resolution would be less than 3 mm at 79 keV. Data rate capability would allow counting to 1M cps. Energy resolution would be comparable to the Anger Camera. Intrinsic sensitivity at 70 keV would be approximately 70%. The resulting system would be fully portable. Actual performance would be verified by comparison to Anger Camera studies under controlled experimental conditions. Experiments to be conducted would measure the improvement in ischemic area determinations using 201T1, the gain in accuracy of blood flow determinations with 133Xe and improvement in ventricular function tests with 178Ta.